Freshwater mollusc diversity in the Kruger National Park: a comparison between a period of prolonged drought and a period of exceptionally high rainfall

Abstract

Most of the previous records of the freshwater molluscs from the Kruger National Park date back to 1966 and earlier. On account of several droughts between 1966 and 1995, a survey was done in 1995 to evaluate the effect of these droughts on the mollusc population. As a result of extensive rainfall between 1995 and 2000 another survey was conducted to establish the effect of a period of exceptionally high rainfall on the species’ diversity of the mollusc population. With the exception of three habitats, an increase in mollusc diversity was recorded for all the other habitats previously surveyed. One of the invader freshwater snail species, Aplexa marmorata, collected in only one habitat in 1995, was found in seven habitats located mainly in the south during the 2001 survey. Another interesting finding was that juvenile specimens of Lanistes ovum, of which large specimens were present prior to 1966 but none found in 1995, were present in the Sirheni Dam in 2001. From this study the positive effect of the high rainfall on the species’ diversity is highly evident.